diff --git a/src/test/util/setup_common.h b/src/test/util/setup_common.h
--- a/src/test/util/setup_common.h
+++ b/src/test/util/setup_common.h
@@ -156,6 +156,22 @@
     //! Mine a series of new blocks on the active chain.
     void mineBlocks(int num_blocks);
 
+    /**
+     * Create a transaction and submit to the mempool.
+     *
+     * @param input_transaction  The transaction to spend
+     * @param input_vout         The vout to spend from the input_transaction
+     * @param input_height       The height of the block that included the
+     *                           input_transaction
+     * @param input_signing_key  The key to spend the input_transaction
+     * @param output_destination Where to send the output
+     * @param output_amount      How much to send
+     */
+    CMutableTransaction CreateValidMempoolTransaction(
+        CTransactionRef input_transaction, int input_vout, int input_height,
+        CKey input_signing_key, CScript output_destination,
+        Amount output_amount = COIN);
+
     ~TestChain100Setup();
 
     bool m_deterministic;
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -325,6 +325,54 @@
     return block;
 }
 
+CMutableTransaction TestChain100Setup::CreateValidMempoolTransaction(
+    CTransactionRef input_transaction, int input_vout, int input_height,
+    CKey input_signing_key, CScript output_destination, Amount output_amount) {
+    // Transaction we will submit to the mempool
+    CMutableTransaction mempool_txn;
+
+    // Create an input
+    COutPoint outpoint_to_spend(input_transaction->GetId(), input_vout);
+    CTxIn input(outpoint_to_spend);
+    mempool_txn.vin.push_back(input);
+
+    // Create an output
+    CTxOut output(output_amount, output_destination);
+    mempool_txn.vout.push_back(output);
+
+    // Sign the transaction
+    // - Add the signing key to a keystore
+    FillableSigningProvider keystore;
+    keystore.AddKey(input_signing_key);
+    // - Populate a CoinsViewCache with the unspent output
+    CCoinsView coins_view;
+    CCoinsViewCache coins_cache(&coins_view);
+    AddCoins(coins_cache, *input_transaction.get(), input_height);
+    // - Use GetCoin to properly populate utxo_to_spend,
+    Coin utxo_to_spend;
+    assert(coins_cache.GetCoin(outpoint_to_spend, utxo_to_spend));
+    // - Then add it to a map to pass in to SignTransaction
+    std::map<COutPoint, Coin> input_coins;
+    input_coins.insert({outpoint_to_spend, utxo_to_spend});
+    // - Default signature hashing type
+    SigHashType nHashType{SIGHASH_ALL};
+    std::map<int, std::string> input_errors;
+    assert(SignTransaction(mempool_txn, &keystore, input_coins, nHashType,
+                           input_errors));
+
+    // Add transaction to the mempool
+    {
+        LOCK(cs_main);
+        const MempoolAcceptResult result = AcceptToMemoryPool(
+            m_node.chainman->ActiveChainstate(), GetConfig(),
+            *m_node.mempool.get(), MakeTransactionRef(mempool_txn),
+            /* bypass_limits */ false);
+        assert(result.m_result_type == MempoolAcceptResult::ResultType::VALID);
+    }
+
+    return mempool_txn;
+}
+
 TestChain100Setup::~TestChain100Setup() {
     if (m_deterministic) {
         SetMockTime(0);